Explained: Why did 4.0-magnitude Delhi earthquake cause such panic?
According to the Delhi Disaster Management Authority, Delhi is located in Seismic Zone IV, indicating a high probability of moderate to strong earthquakes
The authorities put the Monday (February 17) morning earthquake in Delhi at a moderate 4.0 on the Richter scale but it triggered widespread panic in and around the Indian capital. Why?
National Centre for Seismology (NCS) director OP Mishra explained that this happened because its depth lay at just 5 kilometres and also because it occurred in a densely populated region with high-rise buildings.
“It is called a shallow-depth earthquake,” he said. “People panicking was natural.”
Shallow quakes
As the depth of the tremors, with the epicentre at Dhaula Kuan in south Delhi, was relatively on a higher plane, the impact was felt more strongly.
Shallow earthquakes take place at depths of less than 10 kilometres. They are felt more strongly as seismic waves have less distance to dissipate before reaching the surface.
Also read: Delhi | ‘Never experienced such tremors’: Residents as earthquake hits city
Tectonic movements
Mishra also said that the Monday earthquake was not caused by plate tectonic movements but due to "in situ material heterogeneity".
This means it resulted from local geological conditions rather than large-scale tectonic shifts.
Delhi prone to quakes?
Delhi is geographically vulnerable to seismic activity due to its location near the collision zone of the Indian and Eurasian plates.
According to experts, the Indian plate is moving northward at a rate of 5 cm per year, pushing against the Eurasian Plate, a process that continues to build stress along major fault lines.
This activity is the primary reason why northern India experiences frequent earthquakes.
Seismic Zone IV
According to the Delhi Disaster Management Authority, Delhi is located in Seismic Zone IV, indicating a high probability of moderate to strong earthquakes.
A seismic zone is a geographical region classified based on its earthquake risk and historical seismic activity. India is split into four seismic zones — II, III, IV, and V. Zone II has the least risk and zone V the highest.
As part of zone IV, Delhi falls in a high-risk category.
Also read: 4.0 magnitude quake jolts Delhi; PM Modi alerts residents to brace for aftershocks
Fault systems
According to seismologists, Delhi is affected by multiple active fault systems. These are:
Himalayan Seismic Belt: The Main Central Thrust and Main Boundary Thrust in the Himalayan region generate powerful earthquakes, which can have significant effects in Delhi.
Delhi-Haridwar Ridge and Aravalli Fault System: The former is an extension of the Indian plate running beneath the capital, making it prone to intra-plate tremors. The latter, a deep-seated geological structure, has also been responsible for past seismic events.
Soil condition
Much of Delhi-National Capital Region sits on soft alluvial soil, which amplifies seismic waves.
This explains why even moderate tremors feel stronger and cause greater structural damage than in regions with stable rocky terrain.
Major earthquakes
Delhi and its surrounding areas have experienced notable earthquakes in the past.
Delhi and Mathura, located 135 km away, were hit by 7.5-magnitude earthquakes in 1720 and 1803, respectively. The 2015 quake that ravaged Nepal caused major panic in Delhi and northern India. Delhi was also shaken by tremors following a 6.4 quake in Nepal in 2023.
Delhi at risk?
Scientists warn that a powerful earthquake measuring 8.0 in magnitude in the Himalayas is overdue. This could have devastating consequences for Delhi and northern India.
Experts suggest retrofitting older buildings, enforcing stricter seismic codes and improving earthquake preparedness to mitigate damage in the future.
Why do earthquakes happen?
An earthquake is the sudden movement of the earth’s crust at a fault line. It occurs when the Earth’s tectonic plates move against each other, causing friction. This causes the ground to shake violently and sometimes it can even cause landslides, flooding and tsunami.
The location where an earthquake begins is called the epicentre. A quake’s most intense shaking is often felt near the epicentre. But the vibrations can be felt and detected hundreds or even thousands of miles away.
